If you have any interest in old trains, I enjoyed the train ride from Williams. They were running GE diesels from the '70s and cars from the 1940s and 1950s the day I was on it. They run a very old steam engine about monthly with online schedule. It seems well maintained, and runs about 40 MPH max, so it isn't a fast 65 mile trip. It drops you off by the Tovar and south rim and gives about 3 hrs sightseeing if you're on a day trip. Even yesterday people were struggling to find parking spots. Railway RV park near the station takes Passport America offseason at less than $25 per night.
i've camped in park previously but enjoyed this as something different.